<meta charset="utf-8">
(#) No Hard Kotlin Keywords

!!! WARNING: No Hard Kotlin Keywords
   This is a warning.

Id
:   `NoHardKeywords`
Summary
:   No Hard Kotlin Keywords
Note
:   **This issue is disabled by default**; use `--enable NoHardKeywords`
Severity
:   Warning
Category
:   Interoperability: Kotlin Interoperability
Platform
:   Any
Vendor
:   Android Open Source Project
Feedback
:   https://issuetracker.google.com/issues/new?component=192708
Since
:   3.2.0 (September 2018)
Affects
:   Kotlin and Java files
Editing
:   This check runs on the fly in the IDE editor
See
:   https://android.github.io/kotlin-guides/interop.html#no-hard-keywords
Implementation
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/InteroperabilityDetector.kt)
Tests
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/InteroperabilityDetectorTest.kt)

Do not use Kotlin’s hard keywords as the name of methods or fields.
These require the use of backticks to escape when calling from Kotlin.
Soft keywords, modifier keywords, and special identifiers are allowed.

For example, ActionEvent's `getWhen()` method requires backticks when
used from Kotlin:
```kotlin
val timestamp = event.`when`
```

(##) Example

Here is an example of lint warnings produced by this check:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text
src/test/pkg/Test.java:5:Warning: Avoid method names that are Kotlin
hard keywords ("fun"); see
https://android.github.io/kotlin-guides/interop.html#no-hard-keywords
[NoHardKeywords]
    public void fun() { }
                ---
src/test/pkg/Test.java:7:Warning: Avoid field names that are Kotlin hard
keywords ("object"); see
https://android.github.io/kotlin-guides/interop.html#no-hard-keywords
[NoHardKeywords]
    public Object object = null;
                  ------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here are the relevant source files:

`src/test/pkg/Test.java`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~java linenumbers
package test.pkg;

@SuppressWarnings("ClassNameDiffersFromFileName")
public class Test {
    public void fun() { }
    public void foo(int fun, int internalName) { }
    public Object object = null;
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

`src/test/pkg/Keywords.java`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~java linenumbers
package test.pkg;

import org.json.JSONException;
import org.json.JSONStringer;

@SuppressWarnings("ClassNameDiffersFromFileName")
 public class Keywords extends JSONStringer {
    // Using Kotlin hard keyword, but can't be helped; overrides library name
    @Override
    public JSONStringer object() throws JSONException {
        return super.object();
    }
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can also visit the
[source code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/InteroperabilityDetectorTest.kt)
for the unit tests for this check to see additional scenarios.

The above example was automatically extracted from the first unit test
found for this lint check, `InteroperabilityDetector.testKeywords`.
To report a problem with this extracted sample, visit
https://issuetracker.google.com/issues/new?component=192708.

(##) Suppressing

You can suppress false positives using one of the following mechanisms:

* Using a suppression annotation like this on the enclosing
  element:

  ```kt
  // Kotlin
  @Suppress("NoHardKeywords")
  fun method() {
     problematicStatement()
  }
  ```

  or

  ```java
  // Java
  @SuppressWarnings("NoHardKeywords")
  void method() {
     problematicStatement();
  }
  ```

* Using a suppression comment like this on the line above:

  ```kt
  //noinspection NoHardKeywords
  problematicStatement()
  ```

* Using a special `lint.xml` file in the source tree which turns off
  the check in that folder and any sub folder. A simple file might look
  like this:
  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;lint&gt;
      &lt;issue id="NoHardKeywords" severity="ignore" /&gt;
  &lt;/lint&gt;
  ```
  Instead of `ignore` you can also change the severity here, for
  example from `error` to `warning`. You can find additional
  documentation on how to filter issues by path, regular expression and
  so on
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html).

* In Gradle projects, using the DSL syntax to configure lint. For
  example, you can use something like
  ```gradle
  lintOptions {
      disable 'NoHardKeywords'
  }
  ```
  In Android projects this should be nested inside an `android { }`
  block.

* For manual invocations of `lint`, using the `--ignore` flag:
  ```
  $ lint --ignore NoHardKeywords ...`
  ```

* Last, but not least, using baselines, as discussed
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).

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